Process for the production of primary aromatic amines of the benzene series by hydrogenation of their corresponding azo ethers



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Patented Dec. 6, 1932 UNITED ,STATES MICHIGAN PATENT OFFICE! F :l

RALPH P. PERKINsAND PETER s. PETRIE, 0E MIDLAN MICHIGAN, AssIenoRs'ro THE now CHEMICAL COMPANY, 0E MIDLANnIMIcHIGA A CORPORATION "or I PRooEss EoR THE PRoEUcrIoN'oE PRIMARY ARoi/rA'rIc AMINES on THE 'BENZENE. sERIEs BY HYDROGENA'I'ION OF THEIR coR EsPoNEINc Azo 'rrIERs The present invention relates to the catalytic reduction of azo ethers, whereby the azo group is completely hydrogenated and split into two amino groups, each one being attached to an aromatic residue, such hydrogenation accordingly occasioning the vformation of two aromatic amino compounds.

Hitherto, the reduction of azoethers by catalytic hydrogenation of the azo group, has been carried out by means of iron and water, or the like, or by hydrogenation of such compounds in the presence of solvents. For instance, para-diethoxy azobenzene has been catalytically reduced in the presence of decahydro-naphthalene by means of hydrogen, (German Patent No.-406,064). Either of the so mentioned processes involves inherent disadvantages such as the separation, recovery, and loss of solvent and increased cost of production. The first of such processes has the addeddisadvantage of possible intermediate compound formation other than hydrogenation products, and consequent lower quality of product, or greater difficulty of product purification. Furthermore, salts'of metalssuch as iron act catalytically in accelerating the oxidation of amines, whichfurther hinders the easyand inexpensive preparation of a pure product.

We have found that azo ethers can here acted with hydrogen under increased pressures and temperatures in the absence of a solvent, and in the presence-of a hydrogenating catalyst, according to Equation I,

wherein R and R represent aromatic resi-.

dues and X represents an alkyl, aryl, 'oraralkyl group. l q i v To the accomplishment of the foregoing and'related ends, our invention, then, con-V sists of the method hereinafter fullydewhich the principle of theinvention may be used.

V II. cunoOrr:

. d e was obtained.

Application filed September 21, 1929. Serial No. 394376.

For the purpose of illustration, we shall describe below our invention as applied to vthe preparation of para-phenetidine, by by drogenation of para-ethoxy-azobenzene, according to Equation II, 1 V

cmoOnnwNnG Para-ethoxy azobenzene is placed in a bomb capable of being agitated, rotated, or the like,

with the catalyst material which may or may not be supported on a substratum such as I filter-eel or the equivalent, and heated to approximately 120 C. Hydrogenis then passed into the bomb at a pressure between approximately 200 and 500 pounds .per square inch. The bomb is then agitated, such as'by i shaking, until the' absorption of hydrogen ceases,'thus indicating substantial cessation of the reaction, after -which the bomb is opened. The reaction "product is removedv from the reactor, separated from the catalyst mass in any manner, such as by filtration, and the reaction products, namely para-phenetidine andaniline, are separated in any suitable way, suchas for instance bydistillation I under reduced pressure. 7 V

Thefollowing detailed examples are given to illustrate our new and improved method, but it is to be understood that the examples are not to be interpreted as a limitation upon,

our invention. a V a 7 Example 1 340 grams of para-ethoxy-azobenz'ene' was I reduced by hydrogen with the aid of 5 grams of a nickel-alumina catalyst, the latterbeing supported-on filter-eel. -The reduction was performed at approximately (1., at about 450 pounds pressure per square inch, andin' asteel bomb which was agitated byshaking for approximately 6 hours, until the absorp tionof hydrogenceased.- The reaction mix ture was filteredfree from catalyst, and then distilled under sub-atmospheric pressure to separate the, aniline and para phenetidiiie formedinthe reduction; A'yield of 91 ercent of the theoret cal amountof para phenet-f drogen passed in under a pressurerof-500- am le 2 1 240 grams of para-ethoxy-phenyl-azoortho-toluene was treated in a similar manner as in Example 1, the'catalyst being grams of a nickel-filtercel material, the temperature ofreduction 175 to 180 0., the'hypounds per 'square'inch, and the reaction time being 4: /2 hOLlI'S. The products, ortho-toluidine and para-pheneticline, were separated by distillation as described above,the yields be 7 ing 63 and per cent respectively, of the theoretical amounts. c v

' Example? f 6 0 v grams of di-para-diethoxy-azobenzene was reduced by the method of Example 2,'1 n 2 hours at 190 to 200 C. The para-P11811631- 4 dine was distilled as above, after removal of eration.

catalyst. 'A yield of per cent of the theoretical amount wasobtained,

We do not limitour invention to the abovementioned-specificmaterials,or modes of op- 0 Other equivalent azo ethers may be reduced in .asimilar manner, forinstance, eth'ers of the type, a I I wherein R represents an aromatic group, X represents an alkyl, aryl, or aralkyl group,

and wherein the various groups and'the benzene residue may-be further substituted with groups such as alkyl or ether groups.

j-Other hydrogenation catalysts than those mentioned in the examples may be utilized,

for instance, a metal of'the eighth group of Mendeleefs periodic systermor salt or oxide thereof, with or withoutthe presence of a promoter, such asa metal of group.I--B, -II'B', :III.B, or VIIA, o'ra salt or an oxide thereof. Such catalytic material may be employedsingly or'conj ointly with oneor more othercatalytic components of the above menti'oned'series, and maybe supported r othermaterialthan'filterecel,'such as pumice,

etc.;i-We prefer to operate our process using 7 a nickel or a promoted nickel catalyst;

Our modified and improved method may be carried out under pressures between the 'approximatelimits of 100 to 1000vpounds mper square inch, and at temperatures -'beether or any product of itsreduction.

' *Otheritypes-iof' apparatus and other 'construction materials for such'may be employed than abovementioned, since our invention I 1 does not depend upon the apparatus used; H i I V x-wherem R and R represent a1'omatic, esi 1 39;}

For instance, stationary bombs equipped with ether'sfln the absence of'a solvent;

- the stepor steps stated by any of thefollowa suitable means for agitation, or rotating or tubular autoclaves of material substantially inert to the reactants, may be emp ye To summarize, our invention concerns the preparation of amino jethers, such as parapl enetidine, bymeans of the catalytic recluction or hydrogenation underpressure of'azo Other modes of applying the principle of our invention may be employedinstead of 'those explained, changelbeing. made as regards the method herein disclosed, provided ing claims or the equivalent of such stated step or stepsbe employed.

We therefore particularly point out Land distinctly claim as our'invention:. r 1. The methodof making an amino ether, comprising reacting hydrogen with an azo ether, having the general formula;

- j :A1kyl ,O1 R-, N:=N RV wherein R and R representa'romatic residues of the benzene series which maybe further substituted by substituents selected: from thegroup consistingof alkyl and alkoxy sub stituents, the reaction being carried out under' super-atmospheric pressure-,"in' the presence of a; hydrogenation catalyst, in theab.- 9

sence of a solvent, and ata temperaturebetween the melting point of the azo ether and abOut200 G.-- i

2. The method ofmaking-tan aminoether, I comprising reacting hydrogen with an'azo n ether having the general formula, I

the reaction being'carried out under superatmospheric pressure, in the presence of a hydrogenation catalyst, inthe'absence of a V nt, and at a temperature between the i melting' point of 200 C. v v H c 3. The method of making an amino ether, comprising reacting hydrogen with an azo ether, having the general formula, r

wherein R and R represent aromatic res'i- 'duesof the'benzene series, the reaction being carried-out'under a pressure between thelimits of about-100 toabout 1 .000 pounds pres I sure per square inch," in the presence-of a 12 hydrogenation-catalyst, inthe absence of a V solvent, and at. a temperature between the the azo ether and v about nielting point of the azoether and about. 7

4. Themethod of making, an amino ether, I comprising reacting hydrogenwith anfazo THO of the eighth group of the periodic system and salts and oxides of said metals, under a pressure withinthe limits of about 100 to about 1,000 pounds per square inch, in the absence of a solvent, and at a temperature between the melting point of the azo ether and about 200 C.

5. The method of making an amino ether, comprising reacting hydrogen with an azo ether, having the general formula,

wherein R and R represent aromatic residues of the benzene series,- the reaction being carried out in the presence of a catalyst selected from the group consisting of metals belonging to the eighth group of the periodic system and salts and oxides of said metals, and in the presence of a catalyst-promoter selected from the group consisting of metals belonging to the groups IB, IIB, IIIB, VIIB, of the periodic system and salts and oxides of said metals, under a pressure with in the limits of'about 100' to about 1,000 pounds pressure per square inch, in the absence of a solvent, and at a temperature between the melting point of the azo ether and about 200 C.

6. The method of making an amino ether, comprising reacting hydrogen with an azo ether, having the general formula,

wherein R and R represent aromatic residues of the benzene series, the reaction being carried out in the presence of a nickel-catalyst, under a pressure between the limits of about 100 to about 1,000 pounds pressure per square inch, in the absence of a solvent, and

at a temperature between the meltingpoint of the azo ether and about 200 C. V a

7. In a method of making an amino ether, having the general formula,

the steps which consist in reacting hydrogen with an azo ether having the general formula,

V wherein R and R represent aromatic resi- 8. The "method of making para-phenetidine, comprising reacting hydrogen with" para-ethoxy-azobenzene, the reaction 'bemg carried out under super-atmospheric pres sure, in the presence of a hydrogenation catalyst, in the absence of a solvent, and at a'temperature between the melting point of para-' ethoXy-azobenzene and about 200 C.

9. The method of making para-phenetidine, comprising reacting hydrogen with pa'ra-ethoxy-azobenzene, the reaction being carried out under "a pressure between about 100 and about 1,000 pounds per square inch, in the presence of a. hydrogenation catalyst, in the absence-of a solvent, and at a temperature between the melting point of paraethoxy-azobenzene and about 200 C.

10. The method of making para-phenetidine, comprising reacting hydrogen with V para-ethoxy-azobenzene, the reaction being carried out in the presence of a catalyst se-' lected from the group consisting of metals belonging to the eighth group of the periodic system andxsalts and oxides of said metals, under a pressure between 200and 500 pounds per square inch, in the absence 'of a solvent, I

and at about the temperature 120 C. I

11. The method of making para-phenetidine, 1 comprising reacting "hydrogen with.

para-ethoxyezobenzene, the reaction being carried out in the'presenceof a catalyst selected from the group consisting of metals belonging tothe eighth group of the periodic system and salts and oxides of said metals, and in the presence of a catalyst-promoter selected from the group consisting of metals belonging to the groups IB,'IIB,III,B,

and 11 A, of the periodic system and salts and, oxides of said metals, under a pressure within the limits of 200 and 500 pounds per square inch, in'the absence of a solvent, and at approximately 120 C. 1

12. The method of making para-pheneti dine, comprising reacting hydrogen withpara-ethoxy-azobenzen'e, the reaction being carried out in the presence of a nickel-catalyst, under a pressure between 200 and 500 pounds per square inch, in the absence of a solvent, and at a temperature between the melting point of para-ethoxy-azobenzene and about 200 C.

13. In a method of making para-phenetiv dine, the steps which consist in catalytically hydrogenating para-ethoxy-azobenzene .un-

- der super-atmospheric pressure, in the presence of a hydrogenation catalyst, in the absence of a solvent, at a temperature between the melt ng point of para-ethoXy-a'zobenzene and about 200 (1., and fractionally distilling the reaction productunder' sub-atmospheric dine, the steps which consist in hydro- T genating para-ethoxy-azobenzene, under a pressure between about 200 f and about 500'pounds per square inch, at atemperatu're between and Cgand in thepresence, TIL.

of a nickel-containing catalyst, then separating the catalyst from the reaction mixture, and 'fmctionally distilling the latter under sub-atmospheric pressure to'obtain'sepamtely para-phenet idine and aniline.

I Signed by us this. 18th day ofSeptember,

, RALPH P. PERKINS.

, PETER S. PETRIEL 

